Burner flame length control apparatus



June 14, 1960 c. D. MaccRAcKEN BURNER FLAME LENGTH CONTROL APPARATUS Filed Jan. 7, 1954 MMI-Jai( Om INVENToR. CALvm D. MAC CRALKEN PLTTORNEY4 BURNER FLAME LENGTH CNTROL APPARATUS Calvin D. MacCi-aclken, Tenay, NJ., assigner tov Iet- Heet, inc., Englewocd, NJ., a corporation of New' York Filed Jan. 7, 1954, Ser. No. 402,776v

8 Claims. (Cl. Gli-39.28)

This invention relates to improvements in burner control apparatus, and particularly to an improved control for maintaining substantially constant the ratio between the rates of supply of fuel and air to a power-typeuid fuei burner.

Throughout the following description and in the appended claims, the term power burner is used to refer to burners of the type in which combustion-supporting, air is supplied by a fan, blower, ram or the like,Y as distinguished, from so-called -natural draft burners.

certain power burner installations, as in aircraft. and the like, difficulties frequently are encountered in maintaining tr e proper ratio between the supply of, fuelV and the supply of air to the burner to maintain best combustion efficiency. In the case of aircraft installations, for example, a change in altitudeV of the aircraft, with, its accompanying change in air density, will alter any preset adjustment of the fuel-air ratio, requiring readjustment either or the fuel supply or of the air supply if, the correct ratio is to be maintained.

in accordance with a preferred embodiment of the present invention, the fuel-air supply ratio of a power burner is maintained at a preselected value by continuously monitoring the length of the ame issuing from the burner. Upon deviation of the ame length beyond predetermined limits, the fuelv supply to the burner is automatically adjusted to reestablish the preselected ratio.

A more complete understanding of the invention can. be had by reference to the followingdescripn'on of an illustrative embodiment thereof, when considered in connection with the accompanying drawing, the single figure. of which is a schematic diagram of a burner control embodying the invention.

in the `apparatus shown in the drawing, there is ineluded a power-type liquid fuel burner 10 arranged to discharge into an elongated space 12 defined by a cylind'rical casing if. The burner 10 may, for example, be of the high-velocity type, as described in U.S. Patent 2,488,58 by MacCracken, comprising an inner sleeve 16 defining a combustion chamber'17 and surrounded by a coaxial outer sleeve 18. Air is supplied to the burner under pressure by a blower (not shown) to ow into the spa 2d between the sleevesV 16, 18 and thence into the combustion chamber 17 through holes 22 in the inner sleeve i6, to support the combustion of liquid fuel sprayed into the chamber from a nozzle 24 and ignited by an igniter 27.

The fuel nozzle 24 in the embodiment of the invention being described is of the so-called return-flow type, an example of which is to be found in U.S. Patent 2,567,818 by MacCracken. In va return tlow nozzle system, the fuel is supplied to the nozzle at a substantially constant rate through a pump 25 lfrom a supply line 26. At the nozzle, two paths are available to the fuel; one through the nozzle discharge orifice into the combustion chamber i7 and the other back to the supply source (not shown) through a return line 28 and a regulator 30. The rate of delivery of fuel from the nozzle into the tates arent i 2,9-id,?55 Patented June 14, 1960 combustion chamber is controlledV by the amount bled of through the return line 28,V which, in turn, is controlled vby the setting of the regulator 30. An example ofa suitable regulator is given in U.S. Patent 2,590,112 by MacC'racken et al.

It will be understood, of course, that the, burnerv 10 may be` adaptedV to burn gaseous rather than liquidgfuel, in which case a conventional gas regulator would be used.

In the apparatus being, described, the setting of the regulatork that adjusts th'e nozzle output isA controlled by a reversible motor 32. The motor, in turn, is controlled by an electrical system (described hereinafter) which includes a pair of so-calledame electrodes 34a, 34b eX- tending into the combustion space 12'.

The flame electrodes 34a, 34h comprise rods of suitable, heat-resisting and current-conducting material which are mounted in and project through sleeves 36 of insulating material, such. as porcelain. As is well known, ionization. accompanying combustion makes it possible to pass electric current through a iame between a pair of electrodes contacted by the flame. Of course, the chamber wall 14 can constitute one such electrode. Thus, if; the chamber wall and eitherl ofthe electrode rods (34a or 341).) is connected in a suitable electric circuit, current will flow between wall and rod when a ame irnpinges thereon. l

ln the present case, the ame electrodes are. spaced. apart along the path ofiiame propagation` in the combustion space l2. With. this arrangement, -a short. flame will not contact either of the electrodes, a. somewhat longer fiame will play over the upstream electrode 34a but not the downstream electrode 3411', 4while `a still longer flame will irnpingel on both electrodes. relationship. is utilized for control purposes,Y as willV be explained: shortly. l l,

The electrical: system for controlling the, regulator 3.0V includes power supply lines 38 ad'aPtedto be connected. to the usual power supply source (not shown); One of the power supply leads is connected directly to the motor 32'whil'e the other is connected'to the movable contact 4G of' a relay 42. The relay has two fixed'. contacts 44, 46 one of which, (44) is connected to the motor 32 tof complete a circuit for driving the motor in suchl av direction as to cause a decrease in the. fuel output from the nozzle. 24. The other fixed contact 46 is connectedfto. the movable Contact 4S of a second relay S0, which has; a fixed` contact 5,2V vfor completing a circuitV to drive the4 motor 32 in the opposite direction, so as to increase the output of fuel from the nozzle.

Also connected across the power supply lines 38, are aV pair of amplifier circuits 54 for energizing the relays. Among the many suitable relay amplifiers thatY can be. used, a specific example is the type R-l 87 Minneapolis- Honeywell relay circuit. Each of'the circuits 54 is connected with the casing 14 and with one of the electrodes 34a, 34b, the arrangement being such that when ame from the burner contacts either of the electrodes, 34a,'34b, the relay in the circuit connected with, the contacted'electrode will be energized. Both relays are shown in the drawing in deenergized position.

in considering the operation of the apparatus, shownl in the drawing, it should b e noted that for a given supply of air to the burner 10, an increase in the amount of fuel supplied will cause an increase in the flame length, while a fuel supply decrease will decrease the tiarne length. Also, a decrease in the quantity of air supplied, or an air density decrease, will cause ran increase inV the dame length, while anrair quantity or an air density increase will have the opposite eifect. vThe reason for this is, of course, that an excess of fuel for a given quantity of air will cause the combustion area to extend further down- Y 34a, but will not contact the-downstream electrode' 34b.`

Thereafter, the control system will automatically adiustthe fuel supply through the medium ofthe motor andthe regu- Vlator to maintain the same fuel-air ratio. Thus, if theY fuel supply becomesexcessive due to a decrease in VtheY rate orY density of the supply, 'the llame length .will

Vincrease until 'the flame imping'es on the downstream elec-VV trode 34b. This will allow'cu'rrent to ow through the circuito'f the electr'dej34b, resultingin energizationv of theV relay 42. `At the same time, ofcourse, the other relay 50 a1so will @be energized, so that the movable contacts 40, '48 Ywill be inthe position shown in dotted current to said motor, said relays having contacts connected in said last-'named circuit to energize said motor for rotation in one direction upon simultaneous energization of both said relays and in the oppositertdirection upon simultaneous,"dez-energization of both said relays.

4. In a, control system for maintaining substantially constant the ratio between therates of delivery of air and fuel toa power-type uid YVfuel burner, a pair of elec-A tn'cally. conductive electrodes spaced along and Lextend- Y inginto the path along whichrameis discharged from Y said burner, a pair of electric circuits connected one to each'said electrode and each adapted to conductrcurrent upon impingement ofjame on its associated electrode, a relay connected in eachsaid circuit to be energized by current flow therein; and means to control the Vrate of supply of fuel to said burner, said last-named means including Ya control circuit, said relays havingcontacts connected in said lastfnamed circuit to actuate said conlines in the drawing. This will energizeV the motor 32 VtoV trol in accordance with the energization of said relays.

5. In a control system for maintaining substantially constant the ratio between the rates of delivery of air and fuel to a power-type liquid fuel burner, a pair of electrically conductive electrodes spaced along and extending into the path along which ame is discharged from said burnergfa'pair of electric Ycircuits connected one to each said electrode and each adapted to conduct current upon impingement of ameron its associated electrode, a. relay connected in eachV said circuit'to be energized by current 110W` therein, and means to control the rate of supply VYIt can be seen, therefore, that the flame len'gth'con-V Y Y apair'ofielectric circuitsgame detecting electrodes spaced along vthe path' of 'llame discharge from said burner and connected'in saidcircuits to Vpass current therethrough upon impingemen'tof flame onV said electrodes, and means connecting'said circuits jrto said 'control means to decreasel the fuel supply rate Yupon a predetermined increase in length of said ame andto increase said fuel supply rate' uponja predetermined decrease Vin length ofV said llame. 'j Y,2. In 'a`control system for maintaining substantially constant the ratio between the rates of delivery of air and fuel to a power-,typeuid fuel burner, Vin combination, means to controlfthe rate of supply of fuel to said burner, said last-named means' including `a reversible motor and a circuit for supplying current to said motor, a pair of electric circuits, ame detecting electrodes spaced'along thepath of dame discharge from said burner and connected in said'pair of electric circuits to pass current therethroughin response to aine impingement on said electrodes, and means connecting said circuits to energize said motor for rotation in one direction upon a predeterminedincrease inv length ,of` said flame and for`rotation `in the opposite direction upon a'predetermined de-V crease AinA length of'saidmame. l

Vii. Ina control systemYV for maintaining substantially constant, the ratio gbetwe'enthe' ,ratesY of delivery ofai'rV Y and fuel to a-power-type'uid fuel burner, a pair of electrically conductive electrodes'ispaced along and extending intothe path along which llame is discharged from said burner," apair of' electric circuits connected one, to. eachY said electrode `and'each adapted'to conduct current; upon impingement'offlamej on its associated electrode, av relay connected inY each said circuit to be energized by current flow therein, and meansto Control the rate ofY supply of Yfuel to said burner, said last-namedmeans vinf cluding a reversible motor and. a circuit for supplying electric circuits connected one to each said 'electrode and:V

of fuelto said burner, said last-named means including a regulator, a reversible motor coupled to said regulator, and a circuit forV supplying current to said motor, said relays having contacts connected in said last-named circuit to energize said motor for rotation in one direction uponv simultaneous energization of both said relays and inthe opposite direction upon simultaneous de-energiza tion of both said relays; v p Y f VV6. In a control system for maintaining substantially constant the'ratic between the rates of delivery of air andfuelto a powerftype liquid fuel burner, means delining an elongatedcombustion space into which said burnerV discharges, a pair of electricallyconductive electrodes spacedfalong and extending intoV said space, a pair of each adpt'ed toV conduct current upon impingement of flame ongits associated electrode, a relay -connected in each said circuit 'to V,be energized by current ow therein,A

ameauvslt control the' rate Vof supply of fuel to ,saidA burner, said Alast-named means including a regulator, a reversible motor coupled to said regulator, and a' circuitfor supplying current to said motor, said relays having contacts connected in said last-named circuit Vto energize saidk motor for rotation in one direction upon simultane- Vons energization of both said relays and in the opposite direction upon simultaneous de-energization of both said relays.. f Y e '7.-In' a control system'` for maintaining substantially constantf'the ratio Vbetween the rates of delivery of air and fuel to a power-type uid fuelburner, a pair of elec trically conductive electrodes spacedalong and extending intoathe path along which flame is discharged from said burner, apair of. relays, Vmeans connecting said electrodes Y one Yto each-*said relay to energizesaid relays upon` ame impingernent on said electrodes, and meansY to control5 electrically conductive electrodes spaced along and extending into the path along which flame is discharged from said burner, a pair of electric circuits connected one to each said electrode and each adapted to conduct current upon impingement of arne on its associated electrode, means to vary the rate of fuel supply to said burner, said last-named means including a reversible motor and a circuit for supplying current to said motor, and switch means connected in said last-named circuit and controlled by said pair of circuits to energize said motor for rotation in one direction upon simultaneous current flow in said pair of circuits and in the opposite direction in the absence of current ow in both said circuits.

References Cited in the le of this patent UNITED STATES PATENTS Krogh Aug. 25, 1936 Doran Dec. 7, 1943 Gardiner et al Jan. 16, 1951 Goodwin Mar, 1l, 1952 Malick et a1 Aug. 23, 195:5 De Boisblanc Apr. 24, 1956 De Boisblanc July 16, 1957 FOREIGN PATENTS Great Britain Nov. 26, 1952 

